ControlSystems -- transfer functions with delay?

General Usage Performance
7

Yeah I meant u(t)=uinterp(t) which works for me when copying your example. The reason that lsimplot(sys, uinterp, tsim) does not work is that uinterp is an AbstractVector type, and lsim checks the type of u and depending on type will handle it slightly differently. Since it is interpreted as a vector type it is called like a vector which causes an error. Not sure if this is intended, have never used the Interpolation types before so not sure how they interact with stuff.

Internally it looks like this

function lsim(sys::DelayLtiSystem{T,S}, u, t::AbstractArray{<:Real}; x0=fill(zero(T), nstates(sys)), alg=MethodOfSteps(Tsit5()), kwargs...) where {T,S}
    # Make u! in-place function of u
    u! = if isa(u, Number) || isa(u,AbstractVector) # Allow for u to be a constant number or vector
        (uout, t) -> uout .= u
    elseif DiffEqBase.isinplace(u, 2)               # If u is an inplace (more than 1 argument function)
        u
    else                                            # If u is a regular u(t) function
        (out, t) -> (out .= u(t))
    end
    _lsim(sys, u!, t, x0, alg; kwargs...)
end

where if it was handled under the last else clause it should have been fine to call it with uinterp, but as it is now it is caught by the first clause and errors. While the function u(t)=uinterp(t) will be hendled by the third clause and should hopefully work.

Yes it is weird as it is now, and I have opened an issue regarding this so will hopefully be looked over.

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